Electric and hybrid electric vehicles have been available for many years. A hybrid electric vehicle is a vehicle that generally has two sources of energy. One of the sources of energy is electric, and the other source of energy is derived from an internal combustion engine that typically burns diesel or gasoline fuel. A hybrid electric vehicle typically has a greater range than that of an electric vehicle before the batteries need recharging. Moreover, a hybrid electric vehicle is typically equipped with means for charging the batteries through its onboard internal combustion engine.
Generally, a hybrid electric vehicle employs an internal combustion engine and an electric motor to either alternately or in combination provide a driving force for a vehicle. There are several types of electric propulsion systems for hybrid electric vehicles. For example, a pure electric drive system, a series hybrid system, a parallel hybrid system, and a combined series-parallel hybrid system are a few of the designs currently being considered.
Since many of the functions of a hybrid electric vehicle involve an energy storage system (e.g., batteries) and then using this energy at a later time, the performance of the hybrid system is highly dependent on the energy storage system. Some of the factors that are associated with the energy storage system requirements are: power capability, energy capacity, life, cost, volume, mass, temperature, characteristic, etc.